Performance and nitrogen efficiency of Swiss wheat varieties of the 20th century

The average wheat yield in Switzerland has increased from 13dt/ha in 1850 to 60dt/ha today. The present study investigates the factor variety in this spectacular yield improvement. Yield, yield components and nitrogen efficiency efficacy of seven Swiss wheat varieties released between 1926 and 2003 and the French variety Caphorn (released in 2001) have been studied in standardized plot trials for 2 years and at 2 nitrogen fertilization levels (low nitrogen level and medium extenso level). Grain yield shows a constant increase of about 0.24dt/ ha/year, in direct correlation with the year of release of the varieties. This impressive increase is due to the net increase of the number of grains produced per square meter. However, constant improvement of nitrogen utilization by the plants has strongly contributed to this evolution. Understanding of the evolution at both the morphological and the physiological level will contribute, in future, to breed varieties displaying an even more elevated efficacy of nitrogen utilization.